Researchers have created a “biocomputer” out of strands of RNA inside a living yeast cell, and demonstrated that it can be programmed to respond to conditions within the cell by taking specific actions. Like the most basic computers, the RNA device operates on a simple system of Boolean logic—it can be programmed to respond to the commands AND, OR, NAND and NOR.

The invention could have a wide range of applications, researchers say. Bio-computers might eventually serve as brains for producing biofuels from cells, for example, or to control “smart drugs” that medicate only under certain conditions. For example, a smart drug could sample a cellular environment and trigger a self-destruct sequence if disease is detected, [study coauthor Christina] Smolke said [National Geographic News].

For the study, published in Science [subscription required], the researchers designed their RNA computers to detect the drugs tetracycline and theophylline within yeast cells, producing a fluorescent protein as an output. By combining the RNA components in certain ways, the researchers showed that they can get them to behave like different types of logic gates–circuit elements common to any computer. For example, an AND gate produces an output only when its inputs detect the presence of both drugs, while a NOR gate produces an output only when neither drug is detected [Technology Review].

Researchers have been trying to develop molecular machines for the past decade. Recently a different team inserted a DNA device into a living cell and used it to regulate the cell’s production of that same fluorescent protein. That device, however, could not receive signals from the cell into which it was encoded, explained [biomolecular computing expert] Ehud Shapiro. It could merely perform its one operation, completely autonomous from the cell’s normal processes. “The advance in this work is that they show their computation can actually sense molecules in the cell” [The Scientist].